Recent years have seen considerable progress made in the art of laser processing of materials. Lasers can avoid some of the disadvantages of more conventional machining techniques, such as drilling a hole using a drill bit or shaping a material with a rotating end mill. For example, a laser machining process typically does not rely on a rotating machine tool that can wear out due to continued mechanical contact with the work material. There are a myriad of other advantages known to those of ordinary skill in the art regarding advantages of laser process over other techniques. Processing a work material with a laser can include, by way of example and not limitation, machining, cutting, marking, printing, drilling, ablating, vaporizing, heat treating, such as hardening or annealing, as well as many other operations.
However, optimal processing of a material with a laser can require the appropriate selection of laser processing parameters, of which there are several, and each different material can require a different combination of those parameters. Laser processing parameters can include, by way of example and not limitation, wavelength, average power, beam quality, beam spot size, beam divergence, relative traverse speed to the work material, and whether the beam is pulsed or continuous wave (CW). Pulsed beams are extremely useful and often used in laser processing, as they can help ablate and hence remove material while avoiding undue and deleterious heating. However, pulses involve even additional parameters, such as, for example, temporal pulse shape, temporal pulse duration (also referred to herein as pulse width or temporal pulse width), pulse repetition frequency (PRF), energy of the pulse, peak power (PP) of the pulse and spectral bandwidth of the pulse, to name a few.
Unfortunately, establishing a useful laser processing window for processing a particular material can be a largely empirical process involving a fair amount of trial and error and variation of many of the above laser processing parameters. There is typically no comprehensive theoretical approach involving analytical or numerical solutions that allow determination or optimization of the proper processing parameters for processing a particular material. Unfortunately, such variation, if properly empirically explored, can require the use of many different types of lasers, as one laser type is often quite limited in the range of processing parameters that can be varied. The several types of lasers, such as, for example, gas lasers (e.g., CO2 lasers), bulk solid state lasers (e.g. Nd-YAG lasers), semiconductor (e.g., diode lasers) and fiber lasers, as well as different architectures (mode locked, Q-switched, seeded (e.g., by laser diode master oscillator)) and methods of implementation (passive or active mode locking or Q-switching, particular mode locking or Q-switching element), not to mention, perhaps most importantly, the particular active material (e.g., Yb, Nd, Er or Er/Yb, which are often used in the case of fiber lasers) can result in a complex matrix of laser types and implementation details versus resultant capabilities in terms of the aforementioned processing parameters. Even within a given type of laser in which much of the structure is the same, varying a processing parameter can mean procuring a physically different laser. For example, in a mode locked laser the PRF is often a function of the round trip time of light traversing, and hence the physical length of the laser resonant cavity, which is typically fixed for a given physical implementation of a laser. As a further impediment to a full or efficient exploration of a processing window for the laser processing of a material, many of the lasers noted above can be quite expensive and/or large.
It would be a welcome advance in the art to simplify the matrix and to obtain a wider range of operating parameters from a smaller selection of particular lasers or laser types. For example, regarding pulsed lasers providing temporal pulse widths in the high femtosecond to low nanosecond regime (e.g., picosecond pulses), it would be of interest if one or more of the pulse parameters (e.g., PRF, temporal pulse width, pulse energy, pulse PP, etc.) could more readily be varied.
Accordingly, it is an object of the present disclosure to address one or more of the foregoing disadvantages or drawbacks of the art of laser processing of a work material. Other objects will be apparent from a study of the remainder of the present disclosure, including the drawings and claims.